Hi lizashaw,
Orthogel is the gel material that is used in the Nexgel mattresses made by Natura. They have a retail outlet finder on their site to help find the closest outlet. If this isn’t up to date, then the Natura retail outlet finder may be a good option (but I’d call first to make sure that any outlets listed carry the Nexgel). Hopefully one of these two is up to date.
The Orthogel is a foamed gel polymer material made from mineral oil and it’s a “solid rubbery material” with no liquid inside it. It’s also a very durable and strong although I’ve heard rumors that cats’ claws can destroy anything 
There are also quite a few factory direct manufacturers within a 100 mile radius of Hickory if you wish to test other types of mattresses. They include …
www.lakemattress.biz/ Local factory direct manufacturer in Conover. They make a wide range of memory foam and latex and hybrid mattresses. They don’t have finished mattresses at the factory but they will put layers together to give their local customers a good sense of what they feel like. Good quality and selection of different types of layering and good value.
www.originalmattress.com/ Regional factory direct manufacturer with an outlet in Hickory. Makes some good quality and good value mattresses including latex, innersprings, and memory foam. they have two latex models and also have a new memory foam model which uses high quality materials and has good value.
Custom|Specialty|Boat|RV|Camper|Hotel|Rest Home Mattresses|Royale Komfort Bedding|Taylorsville,NC Local factory direct manufacturer in Taylorsville. Makes a range of mattresses including innersprings, latex, and memory foam.
http://www.dilworthmattressfactory.com/ Local factory direct manufacturer in Charlotte that also makes a wide range of matresses with quality materials and good value but focuses on latex. Has memory foam mattresses for those that want it but made by another manufacturer.
http://www.coltonmattress.com/ Local factory direct manufacturer in Asheville. Makes a wide range of mattresses using quality materials including HR polyfoam, latex, and memory foam.
Directory of Verlo Mattress Locations. Find a Verlo Mattress store in your town. Asheville, NC. Regional manufacturer. They also make latex, memory foam, and innerspring mattresses that may have some better quality and value.
http://nestorganics.com/ Asheville. Carry Savvy Rest mattresses which are a high quality “choose your own layer” latex mattress that uses good quality materials (Dunlop and Talalay latex) but may not be in the best “value” range compared to other similar mattresses.
http://www.sleepeasymattressgaffneysc.com/ Local factory direct manufacturer in Gaffney, SC. They make all types of mattresses including innerspring, memory foam, and latex.
High Point Bedding Local factory direct manufacturer in High Point. Makes mainly lower budget and good value innerspring/polyfoam mattresses. No website.
www.walkerbeddingcompany.com/Products.html Local factory direct manufacturer in High Point. Makes some very good value innerspring mattresses using higher quality polyfoam than most. Run by the son of BandL Bedding.
http://www.bandlbedding.net/ Local factory direct manufacturer in High Point who makes quality mattresses using high quality material with very good value. Will make memory foam on request but prefers to focus on materials that won’t soften or degrade as quickly like latex or higher quality polyfoam. Owned by the father of Walker Bedding.
http://reliablebeddingcompany.com/ Another factory direct manufacturer in High Point that has been making a range of two sided innerspring mattresses for over 40 years.
There are some very good choices in this list
Phoenix