Hello
It is great hearing that you business is doing such a sale. Congratulations.
You could have a contract Lawyer as at this current state you would not like to spend on a full time Lawyer who hurts your pockets as a fixed expense.
A Lawyer should be trust worthy so I would suggest having one from your contacts and references.
If the need is really very urgent you should look for the options, meet them personally, express your needs, understand their workings and if you feel all you queries were solve then appoint one of them as a contract Lawyer.

As the type of business isn't mentioned I would suggest someone having:
1. Business and partnering agreements
2. Click-through and Web-wrap agreements
3. User agreements and terms of service
4. Website development agreements
5. Software licenses
5. Privacy policies and related disclosures
6. Advertising placement and insertion orders
7. Co-marketing and distribution arrangements
8. Web hosting agreements
9. Content licenses
10. Application service provider agreements.

Now as per your requirements kindly find one.

All the very best for your future.