Hi Rob,
For prewired "kits" I've used Painless Wiring or similar brands. Performance Improvements, JRP and occasionally Princess Auto are good sources for these. It's definitely far easier to start with one of those kits and work from there, vs wiring up a bare panel yourself. Even with the kit expect to install, mark, remove, and reinstall the kit for a clean installation. You really need to map it out with the Bug as well, since the kits typically expect that you're mounting them near a battery. Splicing into the stock loom for turn signals and ignition will also be required.
If you're looking for "raw" electrical parts...bare fuse panels, spools of wire, connectors, etc. The best source I've used is
www.wayteckwire.com . I usually plan it out, do one big order and then get my smaller resupply from local electrical suppliers. Waytek is great with shipping cross border, and I haven't been nailed with any crazy duties.
hth,
-Dave