K59 are a Hong Kong based company who produce a range of 1/35th scale update sets for a variety of vehicles.

I first saw images of the company's products over on P.M.M.S. in both News reports and Reviews.

Until recently, they weren't terribly easy to get hold of but now they are in stock at Lucky Models from where I obtained details and images:

K59 Product List:

K59-C001: MARDER 2 TURRET REPLACEMENT KIT

K59-C002: M3 WHEEL SET

K59-C003: MARDER 3 (SD. KFZ139) UPGRADE KIT

K59-C004: MARDER 3 (SD. KFZ139) TURRET REPLACEMENT KIT

K59-C005: MARDER 3M (SD. KFZ138) UPGRADE KIT

K59-C006: 2CM FLAK 38 UPGRADE KIT(EARLY) FOR TRISTAR & FLAK PANZER

K59-C007: 2CM FLAK AMMO KIT

As can be seen from the images, these are pretty complete sets. As to availability, they are available from Lucky Model and, as an added bonus, are Post-Free..

The page with the K59 products can be seen: HERE (LINK)