There are a couple of sites for T buckets, tbucketeers and NTBA. I don't know if anyone still build top kits. I have a pile of original T stuff so on the 2 glass ones in the shop I look for the original 23 style irons to install before upholstery and use swap meet bows and replace the wood to get the right look. For top material you need good quality stuff. some places that do boats have UV resistant material. I have seen a few t's that use 1/2 conduit and boat top hardware.