If you need a co-signer that's a sign that you need to do 1 of 3 things:
1. Don't get it.
2. Wait a bit longer to get it.
3. Find another way to get it.
Being told you need a co-signer can be good since it will stop you - even momentarily to look at your current financial situation and evaluate what you can really afford and where you can best put your dollars to use.
Once in a while, if it is an item that you have already calculated for and you know you can realistically handle it but you may not have the greatest or longest history you may just need to go in for the ask. Ask for that better rate, as for another lender, and if you don't get a "good deal" be comfortable with walking away.
There are even ways to obtain a house without a hard credit inquiry.