You can fine many kits here:

http://www.hobbylinc.com/german-plastic-model-airplanes-1:70-1:79-scale

They have 3-4 versions of the JU-52/53.

If you sign up for their points program, You earn points by adding reviews, pictures of your build and buying kits which can be used to discounts the kits. This past year I have saved over $100 due to the points.  Plus they have very good prices on the kits to begin with.

They also have some odd and hard to find kits. Between this, scale hobbyist, and sprue bros. You can locate the kits you want and the best price.

Have you tried West Coast Hobbys - they are in your neck of the woods and do carry quite a few eastern brands.  You can fill out any queries directly on their site:

http://www.westcoasthobbys.com/

regards,

Jack

I actually can't find anything for the JU 53 - did you mean Ju 52 or 52/3m?  If it was just a misspell, you are looking at molds that were created in the late 70's.  The comparison here gives the Heller boxing as being the best of the bunch in 72nd scale:

http://www.britmodeller.com/forums/index.php?/topic/234911019-junkers-ju-523m-kit-comparison/

For the Russian biplanes, have you got any proper names for the types you are interested in?  As mentioned, some eastern manufacturers might have produced something, and that in itself will likely make them a challenge to build.

regards,

Jack

Squadron and Sprue Brothers are really good dealers. If you can't find what you're looking for with either it may be out of production. Sometimes you can find odd stuff at Hobby Link Japan you can't find anywhere else. 

Personally I'd say the best place to pick up kits is at shows. If you don't have one near you or don't want to wait as Brandon said Ebay is probably your best bet, lots of odd and out of production stuff shows up there. Though as an armour modeler you probably already know this .

PS: If you're looking for WWII Soviet stuff you might check some of the Eastern European companies. Though as you probably know from armour some of these companies like Alan are pretty gawdawful. I'm trying to think of some of them but VEB Plasticart and Alan are the only ones that I can come up with off the top of my head. Hopefully ICM, Trumpeteer, and Hobbyboss will continue to model more Soviet hardware. 

Edit: Thinking about it I also came up with Zvezda which is generally good, and AModel which is not so good but buildable.

I usually start looking in those places but thier inventory is limited. I go to Evilbay and look for the scale I want and then aircraft, then I just scroll through whats out there until I see something I like for what I am willing to pay. For 1/72 kits, Airfix makes a ton of birds, as do many others. So, If I searched Evilbay for you wants I would search "1/72 aircraft" and then maybe "1/72 aircraft russian" or "1/72 biplane" etc, etc. That's how I tend to find the kits I am intersted in.

Amazon also has quite a few kits available, but watch the prices, they can be all over the place. The last way I use is Google to see if anyone has review any kits that fit the bill or read forums that mention my wants and get kit names and ideas to searh further from them. 

Good luck and welcome back from the dark side.

BK