Was searching for more info on the Wang (SafeSearch really needs to be on for that particular query!), and I stumbled across this company.
Being the Buckling spring fan that I am, I naturally checked out the IBM section(s).
There seems to be a fair few 122 key terminal boards there.
Hope it's not a repost... if so, feel free to nuke it.
http://www.computertradeexchange.com/inventory/IBMG.html