I can't help with specific 28mm figures but small scale models of them do exist.
On one of my back packing trips to Japan I paid for a "half performance" ticket (2nd act) at a Noh theatre in Kyoto so could not go in until the intermission. Accordingly I waited around in the lobby where there was a display of souvenir masks, pictures and such to buy. Amongst those was a display cabinet of painted character models. Bigger than 28mm wargame minis but certainly not as large as 1/35th.
For a single scenario I would be tempted to look at simple conversions of some of the old Foundry 25/28mm Ashigaru range and a Geisha (Crunch Waffle used to do a beautiful true 28mm model).
If you want more striking characters the 5th Field Miniatures (ex Magnificent Egos) Assassins Bloody Rose & Carnivale, although not Japanese per se, would be a good base for converting, however they are 32mm.
Good luck, I hope you post some pictures when you get the set together.