Sorry it took me so long too! I "volunteered" for another project on the site, and its been eating up waaaay more time than I'd planned, but all for a good cause.
That said, here is some info that you may find helpful:
CHEVY DUTY
Door Screws (original type) for door control, striker, and window regulator are sold by
Chevy Duty. Part number: 18-921 for clutch head, Part number 18-922 for Phillips.
Phillips Flat Head Screw with star washer: Part no. 18-911
www.chevyduty.com TRUCK SHOP
Door handle relay screws: Part no. 47-02205
Window Regulator screws: Part no. 47-02212
www.truckandcarshop.com JIM CARTER
Door Glass lower frame screw kit: Part no. WI-226
www.oldchevytrucks.com Each of these vendors should be able to get you as-original bolts/screws for all parts of your truck. You can download Chevy Duty and Jim Carter's catalogs online; you don't even have to wait for the mail!
There are others, but these were the ones I had handy. Good luck!