Hi,
Can anyone give me a link, from where i can buy 2-2.5 mm strong wire or stainless steel wire for making airplane undercarriages(landing gear) etc.

Sir, Its hard to get in LHS. Try to search in local hardware or spring manufacturer.

Thank you.
Please do not call me sir, I am just 16 yrs old 

Tushar bro you can even get it on cycle repairing shop by asking for strings (steel rod)  used in cycle tyre

Oh, i totally missed that thought, thank you brother.

cycle spokes get bent.
Use spring steel or rickshaw spokes (much thicker)

Thank you for the reply.