Have 2 lensboards for sale. They fit the Beseler 23 or 45 series enlargers. Both have the standard 39mm hole. One has a slight recess on the front and gives a bit easier focusing with 50mm on 11x14 or larger prints on the 23C. $25 for the pair + $5 for US shipping. Or $12.50 plus $5 ea. I can take paypal.
I also have 39mm lock rings @ $5 ea.