I think it may be a bad cdi, but doublecheck all you connections and make sure all your fuses are in tact.
If you do need a CDI, take a look on ebay: 1988 trx300 cdi items - Get great deals on eBay Motors items on eBay.com!
There are a few in the community. You can go to the members page: http://www.quadcrazy.com/browse/ and to the top right of the box, there is a search. You can filter it to MD, then see if anyone is around you... Enjoy!
Welcome to QUADCRAZY! You can use the member search and pick CANADA...there are 270+ members... Take a look: ATV Rider Search » QUADCRAZY ATV Community
Here are some pretty good articles that explains the ignition system of an atv and troubleshooting:
ATV Electronics series Part 1 - ignition systems: Off-Road.com
ATV Tech Tip: Diagnosing no spark or weak spark | ATV Mag Blog
* Added year and issue to thread title.