Make sure you buy a suitable chassis
The common parts in the Honda Cadet class are the engine and the tyres; thereafter you have a wide choice of what you fit them to.
There are numerous chassis manufacturers but they all have to make their Cadet frames within certain limits such as wheelbase which must be 900mm and a main tube size of 28mm diameter (or imperial equivalent). To avoid endless development and increased cost all chassis must be homologated; this is effectively a type approval system whereby a sample model is checked and measured by the MSA and registered. These approvals are done once every 3 years at which time the manufacturers can offer their new models; the old models do not become obsolete but may be less competitive than the later ones...
Karts you may commonly see advertised include BRK, Gillard, Project One, Wright and Zip, all of which are produced in the UK but there are other imported brands such as CRG, Intrepid, Tonykart and many others.
The brake system follows a similar approval system but any homologated brake may be used on any homologated chassis.