How to synthesize a material at 2000atmospheres?
I will try to give some more information knowing what you added in the comments. As you didn't precise which temperature I can't answer you in a very precise way. 

However as I already said you can try to figure out how a reactor for polyethylene's production is made. If you're able to have access to some engineering literature, then you should have a look to tubular and autoclave reactors. If not you will have to contact someone or a company to explain what you want and get maybe an answer. In any case I doubt that having a reactor able to handle both ultra high pressure and (ultra) high temperature could be cheaper. The main reason is the savety. I bet that if you need such high pressure and temperature, you might use some dangerous chemicals and if not you have the savety and security problems of high pressure and temperature. 

I found something that may be interesting for you here. You can achieve a pressure of 2.000 bars at a maximum temperature of 427 °C. On these reactors you can go up to 10.000 bars but with a lower temperature. 

I would advise you to contact them they might have some solutions for your problem.