Yes, you will need to search and evaluate the vendors for the "Collins filter w/o board." I got mine on eBay from Japan for $103 but he no longer has availability. I can't vouch for this UK dealer and his price does appear to be "too good to be true." I provide the correct part number for the "Collins 500hz CW filter w/o board" so you can search for it. Good Luck!
73,
Howard, W6ZZ
W6ZZ