i found a number of players which can do 48khz but now I have discovered IHIFI and colorfly, I will just buy one of these. Here is a list of rockbox supported players higher than 44Khz sample rate.
PS, I found two COWON/iriver players that plays back 48Khz from rockbox.
i've done the work:
Toshiba Gigabeat S 48Khz
Philips GoGear HDD16x0/HDD18x0 96Khz, 88Khz, 48Khz
Philips GoGear HDD63x0 96Khz, 88Khz, 48Khz
HiFi E.T. MA8 96Khz, 48Khz
HiFi E.T. MA9 96Khz, 48Khz
HiFi E.T. MA9C 96Khz, 48Khz
HiFiMAN HM-60x 96Khz, 48Khz
HiFiMAN HM-801 96Khz, 48Khz
Apple iPod 1g/2g 96Khz, 88Khz, 48Khz
Apple iPod 3g 96Khz, 88Khz, 48Khz
Apple iPod Mini 1g 96Khz, 88Khz, 48Khz
Apple iPod Mini 2g 96Khz, 88Khz, 48Khz
Apple iPod Nano 2g 96Khz, 88Khz, 64Khz, 48Khz
Apple iPod Video 48Khz
iriver H10 20GB 96Khz, 88Khz, 48Khz
iriver H10 5/6GB 96Khz, 88Khz, 48Khz
Onda VX747(+)/VX777 48Khz
Samsung YH-820 48Khz
Samsung YH-920 48Khz
Samsung YH-925 48Khz
Sandisk Sansa c200 series 48Khz
Sandisk Sansa e200 series 48Khz
Tatung Elio TPJ-1022 96Khz, 88Khz, 48Khz