If you have misplaced your copy of your T4A(P) slip, you should be able to get a copy of it from CRA. These slips were to be issued by the end of February, if you are signed up for CRA's My Account service, you can sign in and print it out from there. Also if you use the AutoFill service and import your tax information, that slip should import directly in TurboTax for you. 

If all else fails, you can call CRA and after verifying who you are with information from a previously filed tax return, they will release the numbers to you over the phone. 1-800-959-8281 

CRA information on obtaining slips can be found here: https://bit.ly/2U4F7bG