Buy limit order triggered by bid price (filled at ask price), any brokers?

Hi traders,

I have started practicing with the trading platform (Pepperstone ctrader) after much backtesting and I have come across an issue.
In order to execute a limit BUY order I need to specify an ASK price at which the order is triggered. This ASK price is obviously calculated by doing the following:
-obtaining the preferred BID entry price from the chart
-adding the spread

Straight away I started wondering why I cannot specify a BID price at which the order is to be triggered, because in this case I wouldn’t have to ASSUME the spread each time.

I have asked the broker and they said what I am looking for is possible but only for STOP orders and STOP LIMIT orders. It is not available on LIMIT orders which I use for trading bounces.

Does anyone know a way around this or a broker that allows this?
I have done some searching online and a three year old topic on another forum showed that this is indeed an issue for some people and that only a few brokers offer this.