While there are different 'series' of the SME 3012 version one can always find extra weights on ebay.uk. So whatever of Ortofon SPU carts or the FR-7 kinds , the cart weight should cause no problem.
My advice would be: buy the cheapest FR-7 you can find and post this cart to Axel and ask for the line contact stylus pressure fitted in the (new) aluminum cantilever. To 'retip' an old FR-7 means to glue whatever stylus in the existing cantilever. Whatever glue between the stylus and the cantilever is a suboptimal solution.
My advice would be: buy the cheapest FR-7 you can find and post this cart to Axel and ask for the line contact stylus pressure fitted in the (new) aluminum cantilever. To 'retip' an old FR-7 means to glue whatever stylus in the existing cantilever. Whatever glue between the stylus and the cantilever is a suboptimal solution.