On the budget side, there's 3D printable inserts that accept lenses from a cheap pair of Zennioptical glasses.

I got mine from VROptician whose were a bit pricier (maybe $80?). There were some cool options for magnetic ones, but I don't change the lenses enough for it to be worth the extra cost. It'll be interesting to see what Apple charges for theirs.

Most existing headsets have support for adding just the lenses. One example https://vroptician.com/