just found this on amazon. Now the "cheap" TB-enclosures start showing 2*2.5"-drives. Could be enough for many.
http://www.amazon.com/gp/product/B00D4EBIV4/ref=pe_171920_112306500_em_1p_5_ti
// DL
http://www.amazon.com/gp/product/B00D4EBIV4/ref=pe_171920_112306500_em_1p_5_ti
// DL