Is there a way to correct my squat technique?

[DanP]

Sorry, no vid, but I think I can articulate the problem fairly well. I tried squatting for the first time in a couple of years today and used pretty light weights as well as a box. As before, I couldn't keep from bending too much at the waist and absorbing the squat in my lower back on both the down and up. This had always been the case and I believed it was due to tightness in my hamstrings. However, I realized today that it isn't so.

The problem is tightness/lack of flexibility in my arms/shoulders/chest. When I situate myself such that the bar is across my back and my hands are holding it I end up essentially pulling the bar into my body, causing buckling at the waist. It's a situation where something has to give, and if it's my arms, then they won't be balancing the bar and it'll fall. I don't have this problem with goblet squats since my hands are out in front, not pulled back.

The two solutions I've thought of are 1. continue doing goblet squats instead, though eventually the weight of the available dumbbells will become a limiting factor or 2. see if I can convince my gym to acquire one of those squat bars that has the little handles jutting out from the side, as then I'll be able to position my hands as they'd be for a front squat but still do a back squat. Other than that, I'm open to ideas in how to correct this form.