aftermarket remote unlock

[barf]

I liked my first ProStar, it was a Limited that came with a factory keyfob. I miss having that, so I bought a remote unlock system online for less than $30. This is going into an LT625, but most Internationals are probably the same. I can't just wire it in behind the dash somewhere, because everything is J1939 or J1708 bus controlled. I'm going to install it inside the driver's door. Unfortunately, it'll only operate the driver's door, but I'm not too concerned. The remote unit that I bought has two internal SPDT relays, one for lock, one for unlock. The only way that I can think of connecting it, is to the power lock itself. In testing it, I found that the 2 wires running into it get positive on one wire, negative on the second to lock, and vice versa to unlock. I can't think of anyway to connect this without using two more DPDT relays, wired as shown in the picture. Anyone know of any better way of doing this?