1) Company must have issued you Form-16 ?. Send those.
2) Also, you must have filed taxes that should also show income under the head salary. Send your ITR returns as supporting document.
3) Did you receive any joining, salary appraisal letters ?. Send copy of all those.
4) Get fresh 1-2 years Bank statement showing your salary credits. Get the statement sign and stamped from bank.
Add a LoE, and explain to them the reason for non-availability of salary slips (you lost it or whatever) . Politely request them to accept the above documents in lieu of salary slips.
All the Best.