This is the way I got it when I was asking around about this:
Theoretically: No you shouldn't.
In practice: Eh, whatever.
Basically I know people from both schools of thought... one being commercial jars are one use only, don't seal proper and can't be fixed and don't risk it. The other is, well, I use it for my family and it seals fine you just gotta be a bit more careful because they explode easier (not as nice of a tempered glass).... personally? I use them for fruits/jellies/jams - things that last a long while... I get spare lids from where lids come from (a mama lid and a daddy lid...).... and then I dip them in hot wax to seal them just a little more. It's the old farming method.
People give me *** for it sometimes... but my good ol' timey awesome Mother in Law uses PLASTIC jars for her stuff and it NEVER goes off and tastes amazing. (I know I know, anecdote not fact).... I only use the good stuff for friends/family and the fun cool jars for personal. Date them so you use them in a year and you should be okay as long as it was processed properly.
I'm fairly certain a greater % of Aussies use wax/commercial jar methods than American though because the jars are so pricey here.
(I just noticed you have no idea where to get diff. sized lids - I used teh internets... but it's an Australian site so I don't think it'll help: kitchendirect.com.au )