Kodak Imagelink, Agfa Copex or Adox CMS 20 will be around 350-400ln/mm but all these micro films have a low iso rate (a real iso 10) and will need a special developer to keep the C.I. in range.
The Rollei ATP1.1 (Advance Technical Pan ) is a bit less suffering with the C.I. and can be used with regular developers around iso 15 and with the special developers iso 25-40 with also 400ln/mm. Further this film is also available in 120 roll film.
Rollei ATP1.1 with the ATP-DC developer:
Rollei ATP1.1 with Rodinal 1+150 E.I. 15 :
Best regards,
Robert