Podcast Player and Bluetooth?
Try Super BT Mono.  It doesn't explicity say that it works for non-AD2P headsets but I believe that's the whole point of the app.  There'd be no need for this app with a headset that has AD2P.  

Edit: Whoops, that's for Froyo only and you are on Eclair.  

Basically you need to find an app that will stream audio over the HSP profile instead of AD2P but I couldn't find one for you.  You have 3 options as I see them:


Get Android 2.2 on your phone and Try Super BT Mono Froyo Pro
Root your phone, load CyanogenMod and try Super BT Mono Pro
Buy a headset that supports AD2P (they can be as cheap as $30)


Sorry I couldn't help more.