I realize it's a strange time to talk about a G.I. Joe Kre-O "void" when the Ghoststriker and Wave 2 Kre-Ons are officially at retail, but the fact remains once those come and go, and the Arashikage Temple makes its appearance, any future iteration of G.I. Joe's Kre-O line is officially up in the air.
Yes, Derryl DePriest did confirm at ComicCon that the line would continue into 2014 at Toys "R" Us which is fantastic news, but without any concrete information, Kre-O fanatics have started to look at other alternatives for their "building block" fix.
Big props have to go to the cadre of Kre-O fans on Twitter like Twitziller, Kenny, Todd, Flag Points, GeeWunner, AT_GIJoe and many others who find some really cool stuff on the outskirts. Toys from companies like Cobi, Character Building and Oxford (which actually is the company that works with Hasbro to produce Kre-O) offer some awesome pieces to compliment your growing Kre-O collection. Of course some of these items are only available overseas, and you need to expect some increased cost due to shipping or dollar conversion, but they exist and they are available. Check out some examples below:
Character Building - Monsters Vs. Zombies "Lab of Doom"
Recreate the perfect Zombie-Viper outbreak scenario with some great alternate heads or use it as Mindbender's lab or a B.A.T. Factory!
Character Building - Monsters Vs. Zombies "Laboratory of Doom"
Yes this one is a bit different than the one above. Looks like a different doorway and some different mini-figures. Very similar set up with just some minor tweaks.
Amazon.co.uk Building Block Listings
I showcased those two specific sets, but a cursory search of building block sets on Amazon's UK site reveals a wealth of decent military offerings, from tanks and anti-aircraft to transport planes.
Character Building - Dr. Who
Made by the same company responsible for the HM Forces military sets also do some great Dr. Who sets that would also be a great source of B.A.T. factory or Cobra base pieces. There is a particular seller on eBay who specializes in these sets.
Character Building sets from Roxy Media on eBay