Policing is kind of a middle ground, for instance Europe and the UN cooperate with Iran when it comes to policing their borders (or at least they did, I don't know what the current status is) but also usually enforce sanctions when it comes to military goods. There is of course greater worldwide focus on missile technology.
It's no secret that Iran tries as much as possible to be independent of any major weapons supplier and they have largely succeeded in that regard, however the still make some purchases outside of Iran.
The major suppliers for missile components include China and North Korea. Iran's relationship with N. Korea used to be a lot more as a recipient but now most experts agree (and as the empirical evidence we've seen can attest to) that Iran has now probably surpassed N. Korea in terms of capability. China of course plays the largest role exporting numerous major systems to Iran for both their conventional strength, asymmetric threat and nuclear/missile program.
Iran made a few purchases from Western countries, but they're not that noteworthy. They include a handful of light-trainers from France in the 90s, naval transports from the Netherlands also during the 90s. The IRIAF acquired helicopters from Canada during the 90s.
But most of their arms purchases remain unreported as Iran is quite adept at sanction-busting using front companies, off-shore offices, fake export licenses, etc.