There was an ad hoc committee of the House of Commons in the mid-2000s, from 2005 to 2011, with an advisory role. The decisions on funding were still made by Treasury Board and the government. Although the agents of Parliament were comfortable with that mechanism, it wasn't made permanent after 2011.
In terms of your question, there are a number of options available for an independent funding mechanism for agents of Parliament. There are examples in other jurisdictions, other Commonwealth jurisdictions, like New Zealand and the U.K., where committees of the House would have the mandate to determine what the budget of the agents of Parliament would be.
Mr. Ferguson proposed a formula connected to overall government expenditures, but there are a number of ways in which this could be done.