As above really. A few options. You can add a mtl tank to your current mod. That will work just fine and something like the nautilus gt wouldn't look out of place size wise
https://www.vapeclub.co.uk/vape-tanks/aspire/nautilus-gt (other vendors equally as good in the recommendations above). Packs of replacement coils run between £7-£11 depending on the vendor.
this will be great but again way bigger than necessary.
You could buy a new smaller mod/tank kit aspire and innokin do great honest but to be honest I would go this simple
https://www.ecigarettedirect.co.uk/vaporesso-orca-solo-plus
£14 with a free liquid. The 0.8ohm coils work fine with 70%vg liquids they are simple to fill, easy to pocket, have three power levels and once set up you don't need to fiddle any more.
If I was to be quiting now I'd probably not move on from one of these as they just work and are cheaply replaced.