Mouse H2 allele sequences
I have also hit this issue. I was interested in full length amino acid sequences for the classical class I mouse MHC alleles. I was able to find a number of them on uniprot but not all. Here is my list below. Interested if anyone knows additional sequences to extend this:

H-2 D


H-2 Db
H-2 Dd
H-2 Dp
H-2 Dk
H-2 Dq


H-2 K


H-2 Kb
H-2 Kd
H-2 Kk
H-2 Kq


H-2 L


H-2 Ld
H-2 Lq