HELP! Items
You can try taking all the pieces to a parts store that has a large selection of HELP! items. You might be able to look through all the blister-packaged clips, and find something that will work, even though it doesn't look anything like the factory item.
Usually, several car manufacturers have similar hardware, since they use common parts vendors, and "Company X" sells the same door handle system to several manufacturers (with different exterior styling, naturally). If GM used the same or similar type clip, you've hit the jackpot, because quite a bit of the HELP! items are for GM's. If your store doesn't stock anything, look at the catalog; there are pretty good photos and descriptions of the full line. The store can order what you need.
Just another avenue to check out...
Good Luck,
JD