Try this website: www.wiseguys-seats.com. They make underbody seat belt supports that work well for original style and after market bucket seats underbody supports. Click on the catalog tab on the left of their homepage and then click on the seatbelt tab on the left and then scroll down to lap belt hardware kit. I used them on my 1965 Belvedere I Hemi style of Bucket Seats. They worked well and are made of high quality materials.

Good Luck