You can combine both old 401(k) accounts into what is called a "rollover IRA". Open the rollover IRA wherever you want to end up, then transfer or rollover each 401(k) account into the rollover IRA. Having a rollover IRA is exactly like having a regular traditional IRA with the additional benefit that it can later be rolled over into a new 401(k).
It's generally recommended to do a "direct" or "trustee-to-trustee" transfer so you don't run afoul of IRS rules about doing two rollovers within a 12 month period. Direct and trustee-to-trustee transfers are not limited and you could do both rollovers in the same general time frame.
If you are currently working at a job that has a 401(k), you additionally may have the option of rolling your rollover IRA into your 401(k). You'll need to check with your employer's benefits management to see if your 401(k) allows this. Some do, some don't. Mine did.
And you're right, as far as I know you can't open your own 401(k) to receive rollovers from your other plan accounts. But a rollover IRA is essentially the same idea.