Microwave Components

One of the more tricky parts of microwave work is finding the parts. While you can buy most transverter parts built and tested, the cost is often high ($500 or more per band) and many people prefer to build their own anyway. With the rise of commercial microwave systems for TV and WiFi as well as communications there's a fair bit of relatively inexpensive gear around these days. It can't all be used "as is" on the amateur microwave bands, but much of it can be modified or if it can't be, at least it can be dismantled and the parts used to build new gear.

eBay

eBay is a pretty good source for surplus microwave gear. Prices aren't always the lowest, but there's a decent selection of stuff and bargains turn up from time to time. You'll find both high priced gear aimed at commercial applications and low priced parts aimed at radio amateurs and experimenters. For example here's what a search currently turns up (click green arrows at upper right for more pages):

Microwave Surplus Stores

These guys might have anything from a ex-military radar system to small project boxes, connectors and power supplies, all at reasonable "surplus" prices.

Dudley Labs - Not cheap, but good selection
Surplus Sales of Nebraska - Radar Test sets and assorted ex-military gear, plus a wide variety of miscellaneous parts
Alltronics - Misc electronics surplus including microwave TV components
AllElectronics - not much microwave stuff, but lots and lots of surplus electronics

New Components (Retail Prices)

These guys may have the semiconductors you're looking for, but you'll pay retail prices.