Re: TMC5160 substitute?
I ordered a pair of these QHV5160 for $17 each. They are the high voltage variants of the TMC5160, but they have extra pins that need to be cut away and they overhang on one end. There might be sufficient pin length that you can leave one end not quite seated and overhanging the next driver. This assumes light duty and you are not using the heatsink. Check your board to see how these are oriented, if they are end to end or side by side. My board is side by side so it was not an issue for me. They claim to have 3000 pcs in stock.
Those 5161 are strange beasts. The external MOSFETS are on a board below and I suspect the chip output is being used to driver the gates of the mosfets, but since the upper board is available alone, I don't know how they break the pin-to-socket-to-pin connection to route the outputs to the gate inputs. The Fysetc wiki shows the upper boards as available separately. The upper board alone can handle 3.5A. I wonder where the power board comes from?