Good question! There are likely a couple of reasons you won't find many off-the-shelf HFT EAs for MT5. First, true HFT relies on super-fast executions and low latency, which MT5 itself may not be optimized for. Second, developing effective HFT strategies is complex and often requires customization for specific brokers and market conditions.
I'd be curious to know more about your HFT approach. Perhaps there are alternative algorithmic strategies that could work well on MT5?