I find that the local hardware store carries many blocks, larger shackles thimbles and sleeves for swaging, as well as cotter pins. I only get the specialized marine equipment at the chandeleries.

Saltwater sailors have the rust factor to deal with and can't always get stainless steel parts at the hardware store. No Problem. Simply use a rust-paint to paint the parts. They not only cover the part with a protective barrier, the paints come in a variety of colours. Just be sure to keep blocks moving freely and you won't have any problem.

Plastic clamcleats are overall cheaper than their aluminum counterparts BUT the teeth on plastic parts tend to wear after a few years thus becoming useless whereas the aluminum is still as good as new.

My philosophy: Buy right the first time and don't get carried away by brand names.