looking to develop an EA on GBPJPY- where to begin?

I have the system backtested and would like to automate it and keep it away in another account on the side whilst i discretionary trade in others.

As far as rules go it's fairly simple , the indicators used are 4 emas, ATR, TTM squeeze. so where could one go to get an EA built? how much would it cost? i'd like it to be on metatrader4 too.

Any help would be appreciated.

How could you sufficiently test it (a few years, a few thousand trades) without having it automated?