I generally stay with the recommended wire, .029 for the Crappie Spinner, but for any other spinnerbait molds, I use what I can find, which is generally .035 to .040 diameter depending on the weight. I use various hooks for that mold, and rarely the one Do It recommends.
I also use .040 to .045 for buzzbaits.
Give hagensfish.com a try. They have several different wires available and will make them for you in custom sizes, but you have to buy a lot of wires. Otherwise, I've bought some from Ebay sellers and the typical sources such as lurepartsonline, Barlow's Tackle, Jann's Netcraft, Rock Island Sports, and Zeiner's Tackle.
For most of the Do It molds, a slight diameter difference doesn't affect the lure much, and they'll still fit in the mold. For example, if you used .028 or .030 diameter wire in the Crappie Spinner mold, it's not going to make much difference. I have made some 1/8 oz spinnerbaits with that mold, using wires that are .030 and longer than the wire Do It recommends, and that still works. Keep in mind that a longer, but slightly thicker wire can still have about the same vibration, when using the same blades. As long as you don't over weight the hardware, they'll still balance and run true, so there's all kinds of things that can be done as far as wire configurations.