Hi Chris, not sure where you are located, but if on the South Coast near Waterlooville, there is a plastics distributor called Ensinger Plastics, in Waterlooville that if you drop in and go into there side office, you can purchase Delrin offcuts of plate and round bar, anything from 10mm thick to 40mm thick and 25mm diameter to 50mm diameter for around a tenner (goes into their tea fund) I have had loads of bits from them over the years. Delrin is the best plastic for boat use as it is not hydroscopic as some nylon plastics are and is also inert (does not swell up with exposure to water) It's what all nylon products for boats are made of including blocks, rollers and deck fittings such as cleats. It is sometimes known as Acetal but it is a sub group of Acetal, as not all Acetals are suitable for exposure to water. (note they also do Tufnol in different thicknesses as well)