So, answered my own question in case anyone is interested:
http://www.ebay.com/itm/New-Velbon-SPT-1-Telephoto-Lens-Support-Splint-Plate-/270903470520?pt=LH_DefaultDomain_0&hash=item3f131ae9b8#ht_4985wt_1141
Wondering if you know where I can find a Velbon Support Rail to pair my 5D with a Carl Zeiss Cinemescope Anamorphic Lens adapter that I bought from eBay. The support I am looking for is pictured here (as is the anamorphic adapter):
[url=http://[url]http://s42.photobucket.com/albums/e307/blackmore1/?action=view¤t=Carl-Zeiss--anamorphic-lens-velbon-support-rail-2.jpg][url]http://s42.photobucket.com/albums/e307/blackmore1/?action=view¤t=Carl-Zeiss--anamorphic-lens-velbon-support-rail-2.jpg[/url][/url]
Thanks for any help.