ANY stock civic motor from 1988-2000 will drop right into your car, so finding one is not a problem.
Quick break down of motors:
I'll just do what is most common and ignore the base model super-economy motors that Canada never got:
88-91 was either D15B2 or D16A6. Both look identical from the outside, D15B2 made 90hp and D16A6 made 106hp.
D16A6 has a bigger bottom end (longer stroke, the mains are 5mm bigger, block is slightly taller) but otherwise the difference is just in the injection type (multiport or throttle body) and cam shaft. Heads are identical. These motors use OBD0 electronics.
92-95 was either D15B7 or D16Z6. The D15B7 looks identical to the 88-91 motors, and actually is identical to a D15B2 with the exception that it has multiport and OBD1 electronics. It makes 102hp. The D16Z6 is the most sought after factory D-series motor. It has more or less the same bottom end as the D16A6 (pistons have more dish though) but the head is completely different, as it has VTEC. It makes 126hp, and visually you can tell the difference between the D15B2, D15B7 and D16A6 be the valve cover. The spark plug wire tubes on the D16Z6 are angled to the front of the car, not the back like the others.
96-00 was either D16Y7 or D16Y8. These have 106hp for the Y7 and 127hp for the Y8. Their bottom ends are weaker, their oil pumps put out less volume and pressure, and the crankshaft has half the oil holes per journal. The Y7 head is non-vtec, other than that i don't know it's strengths and weaknesses. Visually it looks the same as the D16Z6 and D16Y8 (uses the same valve cover). The D16Y7 is multiport injected but uses a intake manifold with a up facing throttle body, so it looks like a throttle body injected car. The D16Y8 is VTEC, head is designed with ports that allow for alot more swirl-effect for the intake. It also has better quench area than the Z6 and as a result uses less timing. The Z6 head is marginally better for performance. The Y8 is built a bit more for economy. All D16Y motors are OBD2.
For 88-91 there was a D15B1 that made 70hp, it was only on the basemodel hatchbacks. Same as a D15B2 but with a crappier cam and restrictor plate. The CRX HF has a B15B6 that was basically a D15B1 but with half as many valves. They just blanked them out. No idea what power it made, but it was very little and it had a 5000rpm redline.
For 92-95 there was a D15Z1 that was really great for fuel economy, it had VTEC but it was tuned for economy (VTEC-E). Also had a wideband O2 stock for really lean a/f mixes. There was also a D15B8 for US hatchbacks, not sure what power it made, it was like the CRX HF and had only 8 valves, just blanked out half of them.
For 96-00 there was a HX model coupe (?) that was also tuned for economy with VTEC-E. Not familiar with it. There was also a GX trim level that ran on compressed natural gas, don't know anything else about them either other than their pistons are great for making very high compression in regular D-series.
So visually it's hard to tell what is what (only two valve covers) unless it has manifolds to help identify it or the model it came out of.
If you want to use your original electronics (cheapest solution) then a D16A6 is going to be the best bet for power vs cost. Trick is finding one that doesn't smoke, most now have lots of hard miles on them. You could also put in a D15B2 or D15B7, you'll be losing maybe 5hp or so with these due to lost displacement but they also like to rev more since they have a shorter stroke. You could use your original D16A6 cam in those, it's a direct drop in and make a bit more power, though the cam timing does get thrown off a bit because of the shorter deck high of the 1.5L blocks. An adjustable cam gear can correct this.
Another option is to buy a D16Z6 with 126hp and convert your car to OBD1 VTEC electronics. A high quality conversion harness that makes everything plug and play is under $200 (though you can find deals or make one yourself for cheap), and the appropriate ECU is around $120.
You can also mix and match block/head/pistons to make your own high-compression motor using really cheap junkyard parts. I had a '90 Hatch back with a D16A6 bottom end with a D16Z6 VTEC head and electronics, this gave me 10:1 compression. It was good for 15.2 at 90mph in the quarter mile.
There's also a plethora of JDM motors available too, ranging from a DOHC ZC, to a triple-stage VTEC single cam (dang y0, dat E36 M3 is hella tyte, son)