In case someone here really wants one... Someone took an incorrect modern container cap, stamped the "BOYCO" logo into it and is selling sets of 3 on ebay for $185!
http://www.ebay.com/itm/201197670761?item=201197670761&viewitem=&sspagename=ADME :SS:SS:US:1120&vxp=mtr
If you want a set of decent original Boyco caps for your running board can set for about 1/3 of that price, just do a search for "Boyco Canteen". You can generally buy them for $15 to $30 on eBay and they have a nice original "Boyco" script cap that should fit your running board cans...