A little, relatively cheap travel router or WAP is handy for times like these. They either connect phones, dongles, or insert SIMs, or all of the above, and usually have an ethernet connection.

Even better to have that functionality in your main router itself, so you can use the phone as a backup connection. Many routers do allow this. Check yours: if it has a USB socket, then it might do too.

Although as a warning: compatibility is be heavily dependent on the phone manufacturer (Apple in particular hate their users being able to do useful things) and the cellphone provider. Many providers specifically ban tethering and will send you angry texts.

Also as a warning: it is REALLY easy to go over your data limit and cost yourself a small fortune when tethering.