Hi Les, welcome to the club.
I think we have very few Alto owners on here and the information on them seems very limited (I've not managed to find a manual on any, although the late models the manual/info will only be available through the Suzuki portal and I don't have excess to this ).
If you don't get any useful responses (unlike mine ) maybe a photo or 3 may help us.
Hi, Just joined this group. From what I can see not many Alto's were ever fitted with a cabin filter but the compartment for it is there above the fan. It's just that the box is sealed and you have to cut out the access slot. There is a youtube vid on what to do. A new door then needs to be fitted and again I think the same fan assy is used on several Suzuki models most of which seem to have the door so should not be too difficult to source one