An apparatus for delivering fluid at a substantially constant flow rate includes a pair of substantially rigid surface elements for defining a volume that is variable according to constrained separation of the pair of surface elements. The apparatus further includes a support member disposed within the volume defined by the pair of surface elements; and a holding reservoir disposed within the volume defined by the pair of surface elements. The holding reservoir is attachably fastened at a first end to the support member and attachably coupled at a second end to the pair of surface elements.