Just came accross this site (via RadCom) and thought I would share it with you all. They have an amazing number of antenna related hardware which is ideal for mounting and building antennas. They even sell aluminium in enough sizes to slide inside each other. Each length is 6′ and they also have a kit of 11 (inc clamps) to build a 60′ vertical.
They have a good collection vertical antennas you can buy, even a mono band 80m!
It is worth a look.