Ending a sentence with a preposition is completely fine. Do it. You can cite the following sources to anyone who says you shouldn’t:*
- For Who the Bell Tolls: One Man’s Quest for Grammatical Perfection, David Marsh
- Fowler’s Dictionary of Modern English Usage, Jeremy Butterfield (editor)
- Oxford A–Z of Grammar & Punctuation, John Seely
- Oxford Guide to Plain English, Martin Cutts
- Penguin Writer’s Manual, Martin Manser & Stephen Curtis
- The Chicago Manual of Style
Sometimes sentences ending in prepositions should be rewritten because they lack impact or read badly, but they are not ‘wrong’. It is only in the most formal of contexts that placing a preposition before its object is a must. In fact, in some situations it is only appropriate for the preposition to come at the end of a clause or sentence (see Fowler’s for more on this).
Don’t ruin your writing trying to obey this ‘rule’. It is not a thing.
* Martin Cutts calls these people ‘fossils’. I couldn’t possibly comment …