Well, they come up on ebay occasionally, but go for about $45 or so (better than $90), but German ebay lists two different sizes that do not correspond and conversion charts vary depending on who prints them!
I've had a similar experience with surplus. The most I ever found was a surplus store in Alabama that carried a bunch of East German helmets, ushanka caps, and flags (but nothing else EG).
I just got this reply from Sportsman's Guide:
Thank you for the E-mail.
I was unable to locate any east german boots at this time. It is possible we could carry them at a later time. You can keep checking in online.
If you have any other questions please contact us.
Enjoy the Outdoors,
I just won a lot of East German uniform items for $14 (strichtarn jacket, pants, mag pouch, and grey webbed belt with DDR buckle). What a deal!