Mattress-wise, your cheapest option is to eliminate that gap with a twin bed doubler.
From the guardian.co.uk
He received patents on the voltage doubler and the 6800 chip layout.
From the en.wikipedia.org
An optical frequency doubler then reduces the wavelength to 526.5 nanometres, which gives green light.
From the newscientist.com
In 1788, William Nicholson proposed his rotating doubler, which can be considered as the first rotating influence machine.
From the en.wikipedia.org
You can also run a real bodge-job LED lightbulb by getting a 12V MR16 fitting LED lightbulb and a voltage doubler circuit.
From the en.wikipedia.org
John Buchanan was a memory designer at Motorola when Bennett asked him to design a voltage doubler to for the 6800.
From the en.wikipedia.org
This on-chip voltage doubler would supply the higher voltage and Buchanan did the circuit design, analysis and layout for the 6800 microprocessor.
From the en.wikipedia.org
A line doubler could not restore the previously interlaced image at bottom center to the full quality of the progressive image on the top left.
From the en.wikipedia.org
Hays reported hearing a rumor that RealD's light-doubler technology, intended to solve some of the brightness issues, is being used by some exhibitors as an excuse to put in a smaller bulb.
From the variety.com
More examples
An electronic device that doubles the voltage or the frequency of an input signal
One who doubles
(Doublers) are pad-like absorbent soakers that can be added to a diaper to increase absorbency. They are useful and extra protection during nights when you need it.
(Doublers) are thick rectangular, oval or contoured (bone shaped) pads that can be placed between baby's bottom and the cloth diaper for extra absorbency. Doublers are a great addition to any cloth diaper for heavy wetters and night time use. ...
(Doublers) additional plating welded over the top of damaged areas on steel or iron hulls or decks to make good any damage. If it is done over large areas then slots should be cut in the plating so that it can be welded to the frames. This is a common way of renovating old hulls. ...
(doublers) Two boomerangs designed, or paired, to return when thrown together from the same hand. They should do so with sufficient separation to allow both to be caught.
Diaper doublers are also known as liners, inserts, boosters, or soakers (not to be confused with wool soakers). They are made of absorbent fabric. Their purpose is to increase the absorbency of any diaper that you use. Some doublers come with the diaper and can be snapped in place. ...
A steel plate installed on an existing structural plate and used as a strengthening base for deck fittings or as a repair of a damaged area. back
Extra layers of material placed to give additional reinforcement and protection for wear.