is there any cheap way to get aux input on our stock radios?

 

nope. the only way to get aux in our radio is to buy a new radio unit. or if you use ipods you can get the usa-spec connector.

 

damn, new radio unit can get pricey

 

There are AUX interfaces like the Blitzsafe HON/AUX DMX V.2X, the PAC aPAC-HON1 or the PAC PXAUX/PGHHD1 but these things aren't cheap and, IMO, you're better off applying the money you'd spend on these things for a new head unit with the features that you want. I'd say the same thing for the iPod interfaces for the OEM HU as well.