Not sure if any of you are still using SenDEC, but there is some company in Rochester selling used units. I picked up one just for a spare for only $20!
They all seem to have Mag strip sensors.
Search eBay for "SenDEC Race Pro" and you will find all 3 they currently have for sale.
Here is one: http://www.ebay.com/itm/SenDEC-Race-Pro-III-Tachometer-2-Temperatures-Lap-Counter-Time-802-908-/160987021932?pt=LH_DefaultDomain_100&hash=item257b93026c&vxp=mtr