adapters for hands free kits

Is there a supplier for adapters for handsfree kits (such as Nokia and Motorola) that allow the handsfree kit to be interfaced with the vehicle's stock radio and entertainment system?  It would appear that there are manufacturers selling them in Europe but I am having trouble finding somewhere to buy them in the US.

I am aware of the Specialty Autosound / Cell-Site models that are available for some Fords and GMs.

I install primarily Nokia HF kits in GM 1/2 thru 1 ton trucks but would like to find suppliers for more adapters so I can do more sanitary installations on a wider variety of rigs.

Also, is there some other recommendations for suppliers besides Tessco?

Thanks,

MasterMarine