I'd like to try and build one f these for fun and usefulness, and give a few to out local Hacker-space as well for use in what ever they deem necessary.
I tried to find suitable parts from eBay/the usual places, but to no avail. Could someone help me out a bit?
How about trying RS Components. I bought some parts there for this diy terminator. The male bnc is just a standard coax solder type bnc and the female one was a panel mount type. For the resistors, I just used a couple of 100R smd ones. Just be careful while selecting the resistor. The size gets bigger as the wattage gets higher (of course), and it may not fit inside the bnc plug assembly.
Parts List (I used):
2512 Thickfilm Chip resistor 100R; RS Stock No.739-7957
Clamp BNC straight plg-RG58A cable,50ohm; RS Stock No.546-4875
NiPt soldered std BNC bulkhead skt,50ohm; RS Stock No.546-4897
DISCLAMER: I am not affiliated with Radio Spares Components in any way. I'm just a satisfied customer.