OK, here's the story.
I spoke to Keysight parts and found that you can not purchase individual parts for the 53131a/53132A. When I needed a new rotary encoder for my 33220A I bought it for under $3.00 US. I don't know if you can still do this with other instruments from them now, I bought the encoder when they were Agilent and I bought just the display for my 34401A when they were HP, it cost me $68!
The display board for the 53131A/2A complete goes for over $1k US! Yikes! I did find some nice people in CA who had a board with display for $100 but the display is weak. So if you need the board itself and have a good display this might work for you. Do a Google search for TopTestDog with the part number 53131-60002, that's the board you want for both these counters and it works with the 181 too as far as I can tell.
Ebay has a reputable seller with one good display left as of May 20, 2016 (I just bought one) for $250 plus $25 shipping.
http://www.ebay.com/itm/271869857776?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AITThey sent me photos of the working board so I could see all the digits lit properly and the display looks strong.
$250 might sound like a lot but I think my counter would be worthless without it as it's fading, so I bought it thinking that we may never see these displays kicking around when we really need them.
Yes, I know the 34401A won't work in the 53132A, but thanks for your concern guys.
Rob