Dead easy to make your own 1/4" -> din cable if you are versed with a soldering iron. Just need to find out which pins the tip and ring are connected to on the din plug end and go for it.
As for the usb y-cable, I've no idea if that is a simple split or if it has any components in y section for keeping things hunky dory.
I just bit the bullet and bought a 3.x Evolver firmware PIC from DSI 14yrs after buying the synth. One of the reasons I left it so long was the cost of postage is half the cost of the chip! Originally DSI were asking use to send our units to them to install the chip, postage paid us. Only now the machine is discontinued and the cost of the PIC is half what it was originally, I finally decided it I'd better grab one before they are discontinued also.
When there is an exorbitant postage fee, I try to order most than just one thing but Dave doesn't have anything but replacement encoders and pots, psu's and manuals for sale on their site. Not even a teeshirt! So I paid $38us for the chip, of which $13 was postage. Not quite as bad as what the cable kit costs to ship, but I know the pain of not wanting to sell a kidney to pay for an item directly from the manufacturer.