As far as I am aware - there are no 'reputable' publishing companies that approach you regarding book chapters - unless you are a notable academic/leader in the field - or you have been recommended by 'word of mouth'. Personally, I would avoid any unsolicited requests for book chapters. If you have a good idea of a book and/or book chapters - then best to do background work which involves checking the catalogues of publishing houses - and submit your proposal to the editing team for their consideration.