I really doubt that...usually shared jeeps mite be available from gangtok till lachen or lachung..And thereon till gurudongmar.only from lachen to the lake..I doubt if you can get a shared jeep!!
Yes, they are available from gangtok, the entire (2N/3D) package costs 3000-4000 depending on your bargain skills! From lachen however, it is difficult to find a commute.