Just the opposite - trying to find the small clips for that era car was near impossible for me - I ended up having to get them from the dealer (almost at $5 a pop, but luckily the parts counter guy hooked me up).

Try going to importeccatalog.com and search for part # O5030-16411 - these should work for your side moulding (they worked on my '75 and the part # is the same for the 77 according to their system).

To install, you have to remove the existing clip (if present), insert the clip, then push down REALLY HARD with a hard object - the little white pin goes in and pushes out the tabs on the inside of the sheetmetal, holding the clip in place. This can be hard on the front fenders where there is no real support on the bottom - I simply held a 4x4 wood block up inside the fender to push/tap against with a small hammer.

Then to install the moulding, just press it firmly onto the clip - it can sometimes help to start the top and then push down to the bottom or vice versa.

Good luck! Made my car look new again ;)

-Phil