Signet XK-50 Tonearm

I think Signet is no longer in the tonearm business, but would like to know if anyone knows where I could purchase an arm tube for the XK-50. I want to get another cartridge and would like to have another arm tube so I want have to remove the other cartridge. I would like to also get another phono cartridge in the $800-$1000 range. Any recommendations. I now have Grado Platinum low output cartridge with the XK-50 tonearm on VPI HP-19 turntable with Monolith phono amp with Monolith power supply. Any information will be appreciated. I listen to all types of music except Opera and Rap. Thanks.
I do remember seeing at least a couple over the years, pretty rare item though.
Good luck,