Up for sale here is this set of 2 (two) Concept preamp jumper plugs. These will work great in a TON of vintage gear, as well as many other brands. The pins are about 18mm apart, center-to-center. These are really nice plugs and will work great in your Concept receiver. They should fit all the vintage Concept receivers and amplifiers. If you have a Sansui, those use slightly smaller ones, which I have here.
US shipping and handling is $7, and international is $21, no matter what quantity you buy. All my small parts are set up for combined shipping, so just use the "add to cart" feature and then check out all at once, and it will combine shipping. If you have any questions, please ask.