Your options really are finance the new home until your existing one sells, or make an offer with a hubbard clause (contingent on sale of existing home). If you go the Hubbard route, be prepared to show the seller that your house has a reasonable chance of selling in the time period of the hubbard. To do this, it should be fairly aggressively priced and well marketed.
There might be a 3rd option that is a variation on the first, seller financing on the new home. You may have to offer an attractive incentive (i.e. points, or higher rate) to make that happen.
If your agent is not representing you in the purchase, or if you are trying to sell your home yourself, then we, as Realtors, are able to lend advice. I'd be happy to answer any of your questions if this is the case, please contact me through the website below.