Fox, 30, was without a club, after spending a brief spell at Halifax in the Championship in 2014.
“He brings pace and power and adds something different to what we already have within the group.
“He is a really good lad, he has played for England at international level and that level of experience will stand us in good stead for the rest of the campaign.”
Fox is available to play for the Dons in the Easter Monday clash with Whitehaven.
Reynolds joins the Dons on loan from Leigh Centurions, initially for a one-month period.
The goalkicking half-back, who can also play at full-back, has found first-team opportunities hard to come by since joining Leigh from Castleford last year.
“Ben needs to play, he is a very good player with a lot of talent and he will defiantly add something to the group during his initial month with us.
“I’d like to thank Leigh for allowing Ben to join us on loan.”