was wondering if anyone made an adapter to convert a weaver rail to a picatinny rail?
Something that might slide overt he top of the weaver rail perhaps?

If the Weaver rail has cross slots that coincide with spaced crossbolts on an aftermarket MIL-STD 1913 "riser" then you might try it, however, if it is not a grossly oversize Weaver rail, the riser will not sit properly at all (cocked towards the fastening side).
If you absolutely MUST convert, then a custom MIL-STD 1913 sleeve can be machined and secured. We had some badass McCann and Son mounts on our M21,s that were machined to Weaver specs back in the day. A custom low profile steel 1913 sleeve was set screwed on. Nobody was the wiser.
Now if you,re just trying to save a buck or two...............................