To the ministry of armaments:
Regarding the rares: There are really no other than the allies, the USA, Italy and the Soviets that can sell you rares. Of these the allies/USA are either at war with you or has a large risk of sinking your convoys if they would want to sell anything. (Gamey: order 50 rares from the US and live with the convoy sinkings, in RL they made the Cash-And-Carry law which effective prevented any trade from other than the Allies as no axis powers had any cash the US would accept and even if they did then they couldn't carry it home on their own ships as the law required).
Italy most likely sells all they can to you, if you check the diplomacy screen they should be less than 4 rares in surplus, to improve their production you might be able to Share technology Chemical engineering with them if they are behind in that tech. This would give around 5 more rare in best case.
Which leave the Soviets, check the diplomacy screen to see if they have a large surplus or less than the 17 they cancelled. If they have more, then you might have to improve relations, sell them some supplies (25) and they might suggest you buy rares by themselves. They wont suggest you buy their rares if you don't have a large positive cash flow. Sell energy to your incompetent allies. This might give 100+ if they have that surplus.
Continuous research ahead rare production, now I can't remember how much rares you have in vanilla and what the bonus is but I think this might give 5-10 extra for each level.
Reduce revoltish in the rare provinces that are in your Reich. This could also give 5+ rares.
All in all if you won't buy from the USA and can't from the Soviets you are in for a bad time unless you capture a huge stockpile in the Netherland, Belgium or France.