There is no way to do this without risk. You have stated your travel is not certain, as you have said, you could be stuck with a revenue ticket and an award ticket.
If your company buys tickets 3 to 7 days out, then they are not normally going to get the best fares, so I suspect they don't want to risk buying a ticket that won't get used.
Of course, TATL last minute in the summer can be pricey and the good Y seating might be gone.
Have you asked them whether you could buy the cheaper ticket and still be reimbursed, because that would seem to be your highest financial risk, as the award would only risk the $150 redeposit fee
I think it is difficult to answer this without knowing your company's policy on reimbursement if you buy the ticket more in advance, and the odds that your work trip will be canceled or rescheduled.