Or if you feel ambitious you could try the home DIY kit put out by a company called Expert Cell DIY. They make a whole kit for the express purpose of replacing the front glass that includes everything you need; tools, instructions, glass and adhesives. Here's the one you'd need.
[link|https://expertcelldiy.com/products/google-pixel-3-4-5-6-7-pro-a-xl-front-screen-glass-repair-kit?variant=39747410886702|Patent Pending DIY Google Pixel Phone Front Screen Glass Repair Kit – ExpertCellDIY|new_window=true]
I got one of these for a Samsung screen that I wanted to attempt, but alas ended up damaging the OLED in the process of trying to separate the old glass so it didn't work for me, but you might have better luck. I'm not sure how much the Pixel 4a screens are going for these days, but at $28 USD the kit might be worth a try; if it works you'd have a spare screen cheap.