Once in a while you can find the L07J tonearm for sale on eBay or elsewhere. Unless you're lucky, that can take a year or so, but I do believe you'd find one eventually. I have never seen a Power Supply for sale separately. However, the schematic is shown in the Service Manual which can be obtained from Vinyl Engine or from the L07D lovers website. In addition to supplying DC voltages to run the motor, the PS also seems to contain important elements of the servo mechanism. So duplicating it is a job for a pro or a very knowledgable hobbyist.
NOS deck is very very rare but in this situation I would say not more than US$2000, but it depends upon how badly you want it. I do love my L07D for sure. One critical factor that you do not make clear: Is the large heavy brass and stainless steel insert that holds the L07J tonearm included? That piece is indispensable for creating the special sound of the L07D, IMO, and does not generally come with the tonearm as a separate purchase. Duplicating it would be virtually impossible. You would end up buying a second L07D just to get that part, if you don't already have it. If you DO have that piece, then yes, any tonearm with the same pivot to spindle distance and the same vertical shaft diameter as the L07J could be used. The collar in the tonearm mount would accept such a tonearm.
NOS deck is very very rare but in this situation I would say not more than US$2000, but it depends upon how badly you want it. I do love my L07D for sure. One critical factor that you do not make clear: Is the large heavy brass and stainless steel insert that holds the L07J tonearm included? That piece is indispensable for creating the special sound of the L07D, IMO, and does not generally come with the tonearm as a separate purchase. Duplicating it would be virtually impossible. You would end up buying a second L07D just to get that part, if you don't already have it. If you DO have that piece, then yes, any tonearm with the same pivot to spindle distance and the same vertical shaft diameter as the L07J could be used. The collar in the tonearm mount would accept such a tonearm.