At present there are no replacement radiators available from LnR.
However, it is pretty easy build your own. Just go to one of the home improvement stores and purchase some 18 gauge wire. Measure your current radiator and each of the stubs, then measure the distance from the matchbox to where each stub connects to the main radiator. Go to the auto parts store and buy the connectors and place them the same distance from the matchbox as your Quad.
I like the connectors the wire has now but for stealth they could be a little bit stealthier. I found some poly stealth wire for sale that I’m going to grab. I was thinking rather than use connectors I might strip the wire at the same spots, solder it, then use liquid electric tape to weather proof it – what do you think?