Few things to note here....
First....Your not going to find someone with a "Production" strut at 10" length; this is just not something that is made for the general market, far too long...
Second... I am not sure what the size and weight of the aircraft is your building but, at 10" long you may want to consider increasing the diameter. 10" at 1/2" diameter (assuming it is a standard tube type oleo strut) will not take much abuse! 10" creates a substantial leverage arm! Suggest at minimum 9/16 diam (can still be made to fit 1/2" trunion)
Third.... You really need to note the weight of the aircraft so that spring loads can be determined for the strut.
Fourth.... What size wheels are you using and, what is the axle diameter of the wheels?