Is there anything that can be done to the splines on window regulators to keep the handle from slipping? Is there some sort of sheet metal that is flexible enough to put on the spline and then slip the handle on? What about something like liquid metal could that be used somehow. I am trying to keep from replacing the regulators.Any ideas are appreciated

Is it the labor or the cost of the regulators that's causing your reluctance to replace them? The replacement job isn't really that difficult, and you can find regulators for no more than $20 (I've got some for 70-72).

That said, you may be able to wrap a strip of foil around the spline several times. Or, coat the spline with epoxy, slip some saran wrap or other plastic film over it, and then slide the crank back on to "cast" some new teeth on. Once its dried, you can remove the handle and inspect. I'm guessing that either of these repairs will only be temporary fixes at best.

I am selling the car and did not want to put any more money in it. Where is the best place to get them for a 69 chevelle?

Post a "wanted" ad in the classifieds. They need to be from another 69, as 68's and 70-72's are different. They can probably be out of another 69 A-body (Lemans, Skylark, Cutlass) as well as a Chevelle.

The other option is ebay. Here's a pair right now, although its listed as 68-69. Best to ask what year they are from.

http://cgi.ebay.com/ebaymotors/68-69-CHEVELLE-MALIBU-WINDOW-REGULATORS-LEFT-RIGHT_W0QQcmdZViewItemQQcategoryZ40018QQitemZ80325 73752QQrdZ1QQsspagenameZWDVW

Make sure that the handle is decent, some really cheap junk handles out there.