2x3 Wasco Skylight replacement

The rough opening in the drywall is 21x29 and without building a pretty big curb I cant seem to find a replacement. Has anyone ran across this and what did you use and mostly where lol…

Skylights come in 2x2 and 2x4.
Everything else is usually custom.

Choose the 2x4.

Check your local Velux dealer, a roofing and siding supplier.