What are my options? I have a motor with no compression so I'm expecting to have to either do valves (not likely) or jug/piston.

Who has kits available online?

The best prices I have seen are at:
http://www.Highrpmracer.com+
If you buy one of their cylinder kits, you better stick with the stock bore, because the cylinder walls are thinner than factory cylinders.

For the best quality try one of the trusted dealers.
https://buggynews.com/a-list-of-trusted-dealers-t17576.html

Also check ebay... they have a ton of great deals there too, and are better than Highrpmracer because they ship quicker and are more reliable. I bought my 39T sprocket from highrpmracer, I got the sprocket but it took a long time (but it was the best deal on the web). My brother is still waiting for his and it's been about 3 weeks + now.

It sucks because it's a 2 hour drive from my house, but it just takes them a long time to ship things. Also, if it says it's in stock on the website don't go by that! I've put things in my cart that are in stock and 3 days later they'll send an email saying that the item is back ordered .

http://www.highrpmracer.com/loncin-part ... -7926.html

That will fit any GY6?

No.
First you need to take off the plastic shrouds to identify weather you have the "A" of "B" type engine.

This thread may be of help:
https://buggynews.com/used-baja-reaction-150-l4vm-t28347.html?hilit=l4vm&start=20

See this one also for more info:
https://buggynews.com/2-bolt-vs-4-bolt-valve-cover-gy6-engines-t31626.html?hilit=%20l4vm

Good Luck!