As dabac noted, rigid forks are cheaper. Older bike shops or a Bike Co-op should have a collection of rigid forks that were take offs from back in the day when rigid MTB owners "upgraded" to suspension forks or from otherwise damaged bikes. Sort through them and find something suitable by matching steerer diameter, adequate steerer length, matching original wheel size and a reasonable approximation to the axle-to-crown length. As he further noted it sounds like you need more experienced help with this project as fork swaps aren't completely straightforward.