*I'm trying to source a drosophila transformation vector (like pCASPER4,
but) with attB1 and attB2 sites, to use to generate transgenic
Have you considered the Murphy Lab Gateway collection?
The most basic ones have either UASt or UASp promoters driving an
untagged protein; you can also get versions with tags.
They can be ordered from the DGRC once you've signed the correct MTAs.
km287 from cornell.edu