eBay has a lot of different tempered glass sizes.
A glass vendor
That would be the best bet.There are some tempered glass panels here: https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313.TR1.TRC0.A0.H0.Xtempered+glass+panels.TRS0&_nkw=tempered+glass+panels&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=tempered+glass&LH_TitleDesc=0
Check on Ikea if it's the same dimensions https://m.ikea.com/us/en/catalog/products/art/90385461/