I made a 1/4 wave ground plane cut to 150 MHz and it works great from 118 through 940 MHz - the fact that it's cut for 150 MHz means it works great on the harmonic multiples at 300 (MilAir band coverage), 450 (Ham just under that and commercial business band from 450 to 470), and 900 (commercial 935-940 but also 855 MHz public safety and even the 770 MHz public safety band to some degrees).
That's my "wideband" antenna and I made it from parts costing about $5 and it works great for me. I also have an OCFD I made for about $12 in parts and that too works surprisingly well across the same frequency range.
For the record: all my antennas are inside my studio apartment since I can't mount anything outside on my apartment building and they all work fine for my purposes.
Spending more money on some doohickey doesn't necessarily mean you're going to get any better reception, especially if the antennas are mounted inside a structure - if you truly want to get better reception with any antenna it's got to be outside, even if that means taking what you've got and hanging it from a tree branch or using suction cups to stick it on the outside of a window.
As for making a sleeve or a container for the receiver itself to be mounted inside, nothing stops people from doing that considering you'll need to get the device some power (relatively easy) and of course the SDRplay devices and other SDR hardware of a similar nature have a limitation to how far they can be from the USB port you'll eventually have to plug them into. If you set up some kind of Raspberry Pi or Arduino hardware to take the SDRplay signal (or whatever SDR hardware you intend to use) you could then use Ethernet for transferring the relevant data or even Wi-Fi which obviously has a much longer reach than any USB cable will, even if you use USB extenders.
