What you're asking for is a FISH (fluorescence in-situ hybridization)
test, and yes you can have this test done. ( This is not a normal part
of a semen analysis that you would have as part of an infertility
workup.)
It is very unlikely, however, that your husband does not have virtually
50/50 X/Y sperm in his semen. This has been tested many times in
many studies. MicroSort specifically studied this among men who
had three or more boys or girls, and had only fathered one
gender. The outcome among these men was still 50/50.
You can call local labs and ask if they will do a FISH test for
you. Unlike a semen analysis, you don't need fresh or preserved
sperm (the FISH process would kill the sperm anyway). So your DH
would not have to actually go to the clinic to give the sample, you
could do it at home and then drive it there, and you wouldn't even have
to rush because again, you don't need live sperm.
I have seen one clinic on the web who says they will do this by mail
(gross, but convenient!). I think it's the Fertility Institute in
Las Vegas (fertility-docs.com) and if I remember correctly it's $350.
Let us know the outcome if you do it, I think it would be very interesting information to know!