Pettistree Hall Farm in Sutton, near Woodbridge, offers riding to children and adults with physical and mental disabilities. The lease ends in August.
Volunteer Sharon Bleese said the charity's horses - which she described as "heroes" - had an uncertain future.
"Riders and their parents have been very emotional," she added.
"They would be thrilled if it were to remain open as it is such an important part of their lives."
The group was initially set up in Hollesley and needs 15 acres of land to carry out its work with about 15 horses and the 200 riders it has on its books.
"We are desperate to find a new home," added Ms Bleese, who believes an indoor riding school could be moved to its new location.
"We're concerned it's now or never, as we're now in June and August is getting closer.
"We've been looking for the best part of year. We've had a variety of discussions but nothing concrete."
Run by 20 volunteers, the group allows disabled people the chance to ride a horse or pony, or to be pulled in a carriage.
"We have quite special horses - they react to the people on them and with them. They are heroes," said Ms Bleese.
"My horse [which Ms Bleese loans to the group] knows the difference between me and a person who is disabled and the riders come to trust the animals.
"When the riders come here they have half to three-quarters of an hour of freedom, and they can move around and feel the wind in their faces."
Hannah Martin de la Torre, whose daughter Elise is one of the group's regular riders, said: "This means so much to Elise and the other riders.
"Riding is so beneficial not only for Elise's core strength but has added so much to her confidence".
The Hollesely group was originally given a five-year lease at Pettistree, which was extended by 17 years.
The farmer who owns the plot told the charity he needs the land back and gave a year's notice in August 2015.
A Riding for the Disabled group fears it could soon be homeless after 30 years as its search for a new home becomes increasingly "desperate".