Try a local camera shop's "bargain bin", they might even have some used ones floating around with the used camera stuff. Just ask
I have NEVER purchased a cable release new, all of mine(about 40 or so, I'm fickle
) have been sourced from the local camera shows to me(I'm in LA), or from various friends/trades/buying,etc over the past few years. Ranging from 3" ones from old folding Kodak's to 60" ones from view camera kits I've parted out.
but if you must buy new, try Gepe or Kaiser releases. Top notch quality-wise, and should last you a long time w/ kind use.