My seat on my bmx turns literally on every bump. If I tap it it'll turn and normally fall off.. The teeth on the seat look to be fairly worn. I don't really want to spend any money as it's just a bike for riding dirt jumps. I was thinking of glueing it but is there any other way? Cheers :)
Its not exactly clear on what materials are involved. It looks like the top piece was designed with an interference fit, and pressed into the tube. I'm guessing aluminum (or is that zinc?) top piece and steel tube? It's possible to braze dissimilar materials together, but it takes some significant prep work. ($$$)
If it's aluminum to aluminum, it would be possible to TIG weld the two together. You could save some costs by removing ALL the paint from both parts within two inches of the joint before bring them to the welder. Obviously you'd have to remove the seat from the mount, and the tube from the bike frame first.
Have you talked to folks who do welding repairs? It may cost a lot less than you think. I know of one welder whose motto is "Tricycles and kitchen chairs have always been free..."
Your not going to find a replacement seatpost that works with the seat.
It may be worth trying to glue it together, but that will only work for any length of time if you prepare the surfaces properly. You'll need to use a wire brush to get down to bare metal. The the seat half you can use a wire wheel in an electric drill or Dremel, the inside of the seat post will be more challenging as you'll need a narrow brush and will have to do it by hand. The surfaces will also need to be cleaned with a solvent.
You could easily spend more money on tools and materials than on a new cheap seatpost and seat. Find out if you have a bike cooperative near where you live that refurbishes old bikes. They are often a good source of cheap parts.