Indemnity bond for unpaid stamp duty and registration on property

Hello, We are planning to buy a flat from a seller. After giving a token amount, and viewing chain of documents for said flat, we realized that Builder sold to a in 1975, a sold to b in 1985, b transfer deed to c in 1990, c sold to d in 1991, d sold to e (seller) in 2011. I(purchaser) will be buying from e (the seller). Out of above 5 transactions for said flat, 1975 & 1985 transaction parties did neither pay stamp duty and nor registered the transaction. 1990 transaction had stamp duty paid but was not registered. Seller is now ready to sign indemnity bond for any future payable on stamp duty and registration (pertaining to 1975,1985 and 1990 transaction). He is not ready to deduct the consideration amount to the extent of current liability of 3lakhs of stamp duty and registration amount of 3 transactions. After talking to few lawyers, we were advised to get indemnity bond signed. That was accepted by seller as well. However, the draft of indemnity bond from our selected lawyer is not seemingly effective. Need help on wordings of this indemnity bond to maximum safeguard my (buyer's) future possible liability. I ask this as I read on Internet regarding a circular making owners of the flat liable for paying and past unpaid stamp duty. Please help.