We do a lot of BudR staining in our lab.
This is our recipe for Boric Acid Buffer :-

Boric Acid Buffer
Stock A: 0.2 molar Orthoboric Acid solution (7.44g in 600ml distilled 
water)
Stock B: 0.05 molar Sodium Tetraborate(Borax) solution (9.5g in 500ml 
water)

Mix 550ml of stock A and 450ml of stock B; pH 8.4.


Hope this helps.  Our protocol is very robust and we haven't had any 
problems with it.  If anyone wants to see our protocol, please let me know.

Nicola Cragg
Epistem Ltd.