Autogeek sells 4inch pads - and they are generally pretty good for pricing. Gloss-it sells 3.75inch pads and backing plate - but they are somewhat pricey.
Better yet the Owner of this forum has great pads and backing plate. The Uber pads are awesome. http://www.detailersdomain.com/4PackUberFoamPad4inch.aspx http://www.detailersdomain.com/theuber3inchbackingplateforrotariesandorbitals.aspx
Phil has good prices but not for the listed items. The best you will find is... Spot Buff Pads Buff and Shine 2 Pack (Means $2.50 per 4 inch pad) Buff & Shine 3" Backing Plate 5/8" Thread Rotary Buff and Shine 3" Backing plate (Made for 4" pads, $8)
Buff and Shine are by far the most outstanding pads I have ever used. Green is so solid. So, as far as backing plate size goes....would this B & S 3.5" be ok for the 4" pads? Buff & Shine 3.5" Backing Plate
Thanks for the comments everyone. I was going to mention "Glimmer Glass Detailing" ""GGD". It was an awesome business that was a sponsor of Club Lexus a few years back, but it changed ownership and since then they stopped offering discount codes and from my experience their customer service has been one of the worst I've experienced. Their prices are excellent, but I don't know if I can trust someone who doesn't ever reply to emails and phone calls.... If someone has a different opinion about GGD, please share!
Don't be one of those people who is a price purchaser (Walmart). Reward good businesses even if the price isn't as competitive. Especially support the forum sponsors first.
I agree.... I'd much rather give an extra few bucks to someone who actually is involved in the detailing community and genuinely helps out fellow detailers than someone who could give a rat's a** about anything but the mighty dollar.